Plastic polymeric derivatives of chloroprene and process of producing the same



Patented M... 11, 1941 PLASTIC POLYMERIC DERIVATIVES OF OHLOROPRENE ANDPROCESS 05' PRO- DUCIN G THE SAME Mortimer A. Youker, Gordon Heights,DeL, assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Delaware No Drawing.

13 Claims.

This invention relates to a new method for making plastic polymers ofchloro-Z-butadiene- 1,3 (hereinafter, for convenience, calledchloroprene) and more particularly to a method for plasticizing thechloroprene polymers made in the presence of sulfur.

Chloroprene polymerized in the massive state in the presence of sulfurand a substituted thiuram disulfide such as tetramethyl thiuramdisulfide, as disclosed and claimed by Carothers and Kirby in U. 5.Patent No. 1,950,439, gives a high yield of plastic product but thereaction is hard to carry out on a large scale because of the difficultyof removing the heat of reaction from the viscous or gelatinous reactionmass. When an attempt is made to avoid this difficulty by carrying outthe reaction in an emulsion, it is found that the thiuram disulfideprevents polymerization, and if the thiuram disulfide is omit-' ted,that is, if the polymerization is carried out. in emulsion in thepresence of sulfur only (as described in a copending application ofCollins, Serial No. 204,305, filed April 26, 1938,) then the productobtained is not plastic. It is disclosed in a copending application ofYouker, Serial No. 176,821, filed November 27, 1937, that elasticpolymers of chloroprene may be rendered plastic by treating them withcertain substituted hydrazines.

drazines must be thoroughly removed after the polymer has beenplasticized. Certain types of non-plastic chloroprene polymers, such asthat produced in Example 7 of a copending application of Starkweatherand Collins, Serial No. 156,518, filed July 30, 1937, (this particularexample is not an embodiment of the invention described in theapplication in which it appears) may be plasticized to some extent byprolonged milling but such a process is generally inefficient andsomewhat costly.

It is an object of the present invention to provide a new and improvedmethod for producing plastic polymers of chloroprene. A more spe- 0cific object is to provide a method for imparting plasticity to polymersof chloroprene obtainable by polymerizing chloroprene in the presence ofsulfur. A further object is to plasticize such polymers of chloropreneto a high degree without extensive milling. A still further object is toplasticize chloroprene polymers without extensive milling and withouttheintroduction of substances which must afterward be removed. A moregeneral object is the provision of a process for producing plasticpolymers of chloroprene which permits of easier handling and shipping ofchloroprene polymers and which renders it practical for users to haveavailable for use, chloroprene polymers having a wider variety ofdegrees of plasticity. Another object of the Although this method is ofgeneral application, it has the disadvantages that the hy- 7[application March 28, 1939, Serial No. 264,581

invention is to prepare polymers of chloroprene which are truly fluid,that is, which are truly capable of flowing under the influence of anyunbalanced pressure however small Other objects will appear hereinafter.

These objects are accomplished by incorporating into the polymers ofchloroprene obtainable by polymerizing chloroprene in the presence ofsulfur, ,one or more compounds of the general formula RSR1, where R isan alkyl, aryl, thiazyl, thiocarbamyl, xanthogenyl, thioxanthogenyl,aromatic acyl, or aromatic thioacyl group and R1 is hydrogen, abase-forming radical, or a group represented by SnR, in which n is awhole number less than four and R is one of the groups represented by Rabove and then subjecting the polymers to conditions adapted to developplastic properties. Thus, the invention includes the development,promotion, and/or acceleration of the plasticizing action of thesecompounds by aging, heating, and/or milling the polymer into which theyhave been incorporated and/or by adding basic substances, for example,amines which give bases with dissociation constants greater than about10- This application is a continuation in part of applicants applicationSerial No. 204,362, filed April 26, 1938.

This process applied to chloroprene polymers prepared in the presence ofsulfur not only plasticizes those that are elastic and substantiallynon-plastic but also increases the plasticity of the more plasticpolymers of this class. One method for the preparation of chloroprenepolymers containing sulfur and suitable for plasticization according tothe present invention is described in Example 1 of the U. S. Patent No.1,950,439 of Carothers and Kirby.

A more convenient method for preparing such polymers is described in thecopending application of Collins already identified. This methodcomprises dispersing chloroprene in an aqueous dispersing medium andpolymerizing the chloroprene while so dispersed in the presence ofsulfur. Preferably the sulfur is dissolved in the chloroprene prior todispersion of the chloroprene. The dispersion medium may be acid,neutral, or alkaline but is preferably neither strongly acid norstrongly alkaline. The latices described in Examples 1 to 37 and 43 to49 of the Collins application, give when coagulated, polymers which aresubstantially non-plastic, while plastic products are obtained directlyin the case of Examples 38 to 42. The method of polymerizing in emulsionis particularly convenient since it can be more rapidly carried out andmore readily controlled when used on a larger scale than can the methodspecifically disclosed in U. S. Patent No. 1,950,439. Therefore, apreferred form of the present invention involves treatment of polymersprepared according to the method disclosed in the Collins application.

The term parts," whenever hereinafter used,

signifies parts by weight.

In these examples and throughout this application, whenever the term"plasticity number" is i used, it refers to the thickness in thousandthsof an inch of a sample .5-cc. in volume in the form of a cylinder inchin diameter which has been heated to 80 C. for minutesand then keptunder a weight of 5 kilograms for 3 minutes at 1 80 C. Thus, the lowerthe "plasticity number," 1 the greater is the plasticity. The termregain" or recovery, whenever hereinafter used, refers to the increasein thickness of the compressed sample which takes place in one minute onremoving the compressing weight and allowing the 3 sample to return-toroom temperature.

The first eleven examples are given in Table I.

The latices used in these examples were prepared as described in thecopending application of Collins, referred to above, (the number of,

the corresponding example in the Collins case is given in parenthesisafter the number in the table) 1. e., 100 parts of chloroprene in whichthe quantities of impurities did not substantially exceed those given inthe discussion below and containing the indicated quantities ofdissolved sul- 1 fur and other agents was emulsified by gradualaddition, with the rapid mechanical agitation secured by repeatedpassage thru a centrifugal pump, to the indicated quantity of an aqueoussolution containing the indicated emulsifying and other agents. Furthervariations in the mentally determined graph. Thus, the polymerizationwas continued until the density corresponding to the yield given in thetable was reached. The approximate times required to reach this stage ofpolymerization are indicated but since they vary somewhat, even whenconditions are closely duplicated, it will be found more accurate to endthe operation when the proper density has been reached rather than aftera given time.

Further polymerization of this latex was then arrested by the additionof 1 part of phenylbeta-naphthylamine and 1 part of tetramethyl thiuramdisulflde dispersed in 10 additional parts of the emulsifying solutionwith the aid of 8 parts of benzene. The latex was then coagulated byaddition of saturated sodiuin chloride solution with the furtheraddition of ethyl or butyl alcohol in Example 11 where coagulation wasdiflicult with salt alone, according to the method disclosed by Calcottand Youker in their application Serial No. 181,602, filed December 24,1937 The resulting coagulated polymer was then plasticized and at thesame time washed and dried by working it first. under running water at6. 0:: a mill with corrugated rolls for from 20 to 30 minutes and thenon a smooth mill at 50 C. for an additional 20 or 30 minutes with theaddition of 0.5 part of phenyl-beta-naphthylamine and 0.5 part oftetramethyl thiuram disulflde until it had reached constant weight. Theplasticity numbers and regains of the resulting plasticized polymers aregiven in the table. The table also gives the tensile strength obtainedafter compounding these plastic polymers with 5 parts of wood rosin, 5parts of zinc oxide and 10 parts of. light calcined magnesia per 100parts 'of plastic polymer and curing in a press for 10 minutes at 151 C.1

, Table I Plasticity fitg? Emulsiiying agent Amount x: Sulfur Temp. TimeYield 83' gzg li and regain C'. Min. Percm! Lba/ag. in.

1(14) Na 019MB 3. 0 300 1. 0 40 180 84 92-0 3450 2(16; N8 steal-ate 4. 6300 1. 0 40 90 85 85-1 3425 3(17 Na naphthenate 3.0 300 1. 0 40 2880 66100-4 2925 4(21) Na hyd rIoaiggate (0.25 4. 0 300 0. 5 B110: 0. 05 40130 90 93-4 4275 per a 5(23) N a hyd oaggtate (0.13 4. 0 300 ,1. 0N81510: 1 0. 05 40 87 103-7 3800 per a Y 6(25) Nlaqalgg;ite (0.25 part4.0 233 0. (NHd B Oa 0. 5 40 120 90 74-3 4475 7 (26) Naisopropylnaphtha- 8. 0 300 1. 0 40 147-12 3200 lene sulfonate.

, 8(30) NaLorol" sulfate..- 3.0 300 1.0 40 86 142-18 3800 9(35) Na saltof sulfated 8. 0 400 1. 0 CS: 10. 0 40 30 90 124-16 3775 oleyl acetate.

10(37) N a salt of sulfated 4. 0 400 2. 0 CB: 10. 0 40 30 84 105-5 2475oleyl acetate. f

11(46) C-cetyl betaine 3. 0 300 1. 0 40 270 73 -8 4850 1 These weredissolved in the aqueous phase. g Lorol" is a mixture of straight chainaliphatic alcohols, with an process are given in foot-notes to thetable. The

dispersion wasthen maintained, in a vessel which 1 could be externallyheated or cooled, at the indicated temperature until the percentage ofthe 1 chloroprene indicated in the table had been polymerized. Thecourse of the polymerization was followed by determining the density ofthe dispersion, which is approximately a linear function 5 of theproportion of chloroprene which has polymerized. The densitycorresponding to any given yield of polymer may, accordingly, becalculated from the densities of the starting materials and of thepolymer or may be read from an experiaverage chain length of about 13carbon atoms, made from cocoanut-oil.

and up to 5.0% of dichloro-1,3-butene-2 may be used with good results.Divinylacetylene should -merization is claimed in the copendingapplicabe substantially absent. When the emulsifying solutions sensitiveto acids are used, and the latices are to be stored for considerableperiods, the total concentration of dichlorobutene and other impuritiesyielding acids on hydrolysis is preferably less than 0.5%. On the otherhand, incertain instances, impurities have favorable effects on someproperties and may advantageously be added or allowed to remain in theseparticular cases. For example, divinylacetylene, although undesirablefrom many points of view, has been observed to improve solventresistance in certain cases. I

Any of the forms of sulfur which are soluble in chloroprene may be used.Ordinarily, .the sulfur is dissolved directly in chloroprene beforeemulsification. Particularly when high proportions of sulfur are desiredit is advantageous to dissolve the sulfur in a solvent such as carbondisulfide or a highly chlorinated naphthalene. The sulfur may also beadded to the water phase in the form of an aqueous dispersion providedconditions are such that the sulfur dissolves in the chloroprene phasein substantial amount before polymerization. In short, any method ofadding the sulfur may be used which produces this latter result. Theproportion of sulfur used is ordinarily from about 0.25% based on thechloroprene, up to the maximum amount soluble in the chloroprene phaseat the temperature of polymerization. Increasing the proportion ofsulfur within these limits increases the extent to which the resultingpolymers may be plasticized.

Further variations in the process comprise polymerization in thepresence of both .sulfur and one or more modifying agents, (sulfurdioxide, hydrogen sulfide, unpolymerizable acid stable organic compoundswhich form monomolecular addition products with chloro-2-butadiene-1,3,under mild conditions of reaction, etc.) such as are disclosed inStarkweathers U. S. application 69,739, filed March 19, 1936;Starkweather and Collins U. S. applications 69,737 and 156,518, filedMarch 19, 1936, and July 30, 1937, respectively, (when these modifyingagents are used with sulfur, the polymer isolated from the latex is, ingeneral, soluble and rather plastic without additional treatment,although it may be made more plastic by subjecting it to theplasticizing treatment disclosed herein) and polymerization in thepresence of sulfur varied in any of the ways disclosed in U. S. PatentNo. 1,967,861 with reference to emulsion polymerization in general,including polymerization in the presence of inhibitors (see US. PatentNo. 1,950,438) and polymerization in the presence of solvents, oils,softeners, film-forming materials, and polymerizable compounds (see U.S. Patents Nos. 1,967,860; 2,029,410; 2,066,329; 2,066,330; and2,066,331). Altho certain of the compounds included by the above generalformula, such as the'thiocarbamates and thiuram disulfides, greatlyinhibit the polymerization of chloroprene in emulsion in the presence ofsulfur, the remainder of the compounds, in general, have little or noinhibiting effect and accordingly they may in many cases be addedadvantageously before or during the polymerization. Thus, whenchloroprene is polymerized in the presence of sulfur and of compoundssuch as the mercaptans, the dixanthogens, the bis-thioxanthogens and thearomatic acyl polysulfides, a plastic product results directly. Thepresent invention is limited, however, to the addition of these agentsto the chloroprene polymer. Addition of mercaptans before or duringpolystarting dispersions tion of Collins, referred to above Anyemulsifying agent may be used to assist in dispersing the chloroprenebut naturally those giving fine and permanent dispersions are preferred.The medium in which the chloroprene is polymerized may be eitheralkaline, neutral, or acid. Of course, it will be necessary to choose anemulsifying agent which is effective in the medium in which thepolymerization is to be carried out. Preferred emulsifying agents fromthe points of view of both eoono y and efliciency are the water solublesalts of 'darboxylic acids containing long hydrocarbon chainsorpolycyclic systems for example sodium oleate and especially thederivatives of rosin such as sodium abietate. The amount of emulsifyingagent used will, of course, depend upon the effectiveness of theparticular agent, the concentration of the emulsion and the degree ofstability desired. In general, the emulsifying medium used will containfrom about 0.2% to 6% of emulsifying agent based on the weight of theemulsifying medium, although still lower or higher amounts may also beused.

It is often advantageous to carry out the polymerization in a medium ofdifferent hydrogen ion concentration from that resulting from dissolvingthe emulsifying and other agents in the water. 'In addition to itseffect on modifying agents and stability, the hydrogen ion concentrationof the medium also has in many cases an ultimate effect upon theplasticity and other properties of the products of the presentinvention. The present invention in its broadest aspects is not,however, limited as to the hydrogen ion concentration of thedispersions, If desired, the polymerization in emulsion may beaccelerated in any of a variety of ways, such as by increasing thereactiontemperature, or the concentration of the emulsifying agent, orby adjusting the hydrogen ion concentration, or by the choice of anemulsifying agent, or by the use of catalysts, such as soluble compoundscontaining the peroxide nucleus.

A high concentration of chloroprene in the usually makes it difflcult tomaintain the desired temperature and low concentrations require largerreaction vessels and more coagulant and accordingly the preferred rangefor the concentration of chloroprene in the emulsions is 20% to 65%although both higher and lower concentrations may be used. Thechloroprene may be dispersed in the emulsifying medium in any desiredmanner but is is preferable to so emulsify it as to form very fineparticles. Polymerization may 'be effected at temperatures ranging from0 C. to 100 C. and above but the preferred range of polymerizationtemperatures is about 20 C. to about 80 C. It has been observed thatincreasing the temperature in addition to speeding up the polymerizationalso reduces the tendency of both the cured and the uncured polymer tobecome stiff and hard when kept for long periods at low temperatures.The mixing of the various constituents as well as the emulsification andpolymerization described above may also be carried out continuously,according to the procedure described in the copending application ofStarkweather and Collins, Serial No. 156,518, filed July 30, 1937. Infact, by following the procedure described in a copending applica-' tionof Walker, Serial No. 154,212, filed July 17, 1937, the whole procedure,beginning with the mixing prior to emulsiflcation and continuing thruthe further steps described herein including coagulation, washing anddrying of the polymer, may be conducted continuously.

, The products produced by the process illustrated in the above exampleswill naturally vary 5 considerably in their characteristics, dependingupon the particular conditions employed. The

, extent of polymerization (proportion of the chloroprene consumed) hasbeen found to be one of the factors which affects polymer whenplasticized by in this application. Thus, a

the behavior of the the process disclosed lower yield is usuallyassociated with greater plasticity but somewhat inferior strength. Whenthe polymerization has proceeded to the extent experiments to correspondsired, it may be stopped by found by preliminary to the properties de--the addition of an antioxidant, such as phenyl-beta-naphthylamine or bythe addition of one of the compounds disiclosed for that purpose inWalker U. S. application, Serial No. 154,212, filed July 17, 1937, forexample, a thiuram disulfide such as tetramethyl thiuram disulfide. Inaddition to serving to ar-' rest polymerization,

the compoundsdiscl other purposes, for

both the antioxidant and osed by Walker also serve example, protectingthe polymer against the effect of oxygen in the case of the former and,in ing to plasticlze the process described he are effective for theagainst the action the case of the latter, assistpolymer accordingto therein. Antioxidants which protection of natural rubber of oxygen alsofunction in the case of thepolymers oi the present invention. Inaddition to phenyl-beta-naphthylamine, the

5 following have been found particularly useful:

N-acetyl-N-phenyl-p-phenylene-diamine Di- (p-methoxy-phenyl) -amineDi-phenyl-p-phenylene-diamine p-Tolyl-sulfonyl-amino-phenyl-p-tolyl-amine 40 p-Etlioxy-phenyl-beta-naphthylamine4:4'-Di-anilino s Diphenylamine ymmetrical di-phenyl-thioureaPhenyl-alpha-naphthylamine The amounts of the antioxidants and of thecompounds disclosed by Walker which may beadded to arrest thepolymerization are illustrated in the above examples but since theseproducts are also used for other purposes as disclosed above, theamounts of each which may be added are discussed more fully hereinafter.

When either one or both agents are added to the polymer dispersion,preferably the agent or agents are first emulsified in water, forexample,

in the same aqueous medium in which the polymer is dispersed.Frequently, they are dissolved in benzene or other suitable solventsbefore emulsification. It is particularlyconvenient to use two or morereagents whose mixtures melt below ordinary temperature. Thus, a mixtureof two antioxidants maybe parts of diphenylamine an used, for example,45'

d 55 parts of phenylalpha-naphthylamine give a liquid mixture which maybe readily dispersed in an emulsifying solution without the use ofsolvent and may, be

v used in place of the dispersion of a benzene solution ofphenyl-beta-naphthylamine described above.

brought about b in some cases with hol, as described in Calcott andYouker.

available 1 78 electrolyte or this purp s and parti Many other.procedures are ose, such as the use of other cularly coagulation by ex-'in thin films to low temcation of Calcott and Starkweather, Serial No.107,332, filed October 24, 1936. In fact, the latices described aboveare even more suitable for 5 this purpose than those prepared accordingto Y the patent applications of Starkweather and Collinsalready referredto, since the former yield films which are stronger, more rigid,a'nd'freer from tack and hence are more easily carried 10 through thewashing and drying operations.

Although in certain cases there may be some reason for allowingthe'emulsifying agents to remain in the polymer after coagulation, it isgenerally preferable to remove substantially all 1 of them before thefinal milling. This may be accomplished in any desired manner, forexample, by washing the polymer in large masses with warm water oncorrugated rolls or in thin films of the polymer with sprays of water,assisting 20 the extraction, if it is desirable,.by using a solventwhich dissolves the emulsifying agent but not the polymer such asalcohol, acetone, etc. Milling, may bring about a sufficient drying ofdeemedsatis- 25 polymer may be additionally dried, for example, bypassing it in contact with a current of warm air. Milling on a rubbermill also assists in removing volatile material from the polymer butother means for effecting-its removal 30 are often resorted to, forexample, as is disclosed in the copending application of 'Calcott andStarkweather Serial No. 107,332, filed October 24, 1936, and referred toabove, for example, washing the polymer in thin films with solvents. 35

The above description sets forth, both in general and in some detail,the preparation of polymers to be plasticized according to the presentinvention. It will be understood, however, that the additional detailsset forth in the copending 40 application of Collins, Serial No.204,305, filed April 26,. 1938, which describes emulsion polymerizationof chloroprene in the presence of sulfur, are incorporated in thepresent application byreference, so that this application is notstrictly limited to the above described method for preparing polymers tobe plasticized.

The method of carrying out the invention may also be further varied, asdisclosed above, by starting with a polymer prepared in the massive 50state, for instance according to Example 1 of U. S. Patent 1,950,439. Itmay also be varied by using other compounds of'the above general formulain place of tetramethyl thiuram disulfide, by varying the proportion ofthe compound of the general formula and the conditions under which it isused, and by the presence of certain auxiliary plasticizing agents.These variations are. illustrated in the following examples and in thediscussion which follows:

I Example 12 An elastic polymer of chloroprene was preto U. S. Patenting for 10 minutes, the product had a plasticity 76 cent ofphenyl-beta-naphthylnumber of 142 and a recovery of 27. Incorporating 1%of magnesium oxide reduced these figures to 125 and 14. On repeating theprocedure except that no disulfide nor ma nesium oxide were used, theplasticity number was 237 and the recovery was 262.

Example 13.

A polymer of plasticity number 87 was obtained by following theprocedure used in Example 12 but stopping the polymerization whenone-half the chloroprene had been consumed and removing the unchangedchloroprene by extraction with alcohol. When this polymer was milledwith one per cent each of tetramethyl thiuram disulflde,

phenyl-beta-naphthylamine, and magnesium oxide, the plasticity numberwas reduced to 30.

Example 14 Benzothiazyl disulfide Example 16 A latex was made asdescribed in Example 6 except that one-half part of the sodium salts ofthe acids obtained by condensing naphthalene sulfonic acids withformaldehyde according to U. S. Patent No. 1,191,480 was used along withthe sodium abietate as emulsifying agent. The latex was treated with adispersion of one part of phenyl-beta-naphthylamine, neutralized withacetic acid, and coagulated in the form of a continuous sheet, asdescribed in a copending application of Calcott and Starkweather, SerialNo. 107,332, filed October 24, 1936, by freezing it in a thin layer onthe surface of a rotating, internally cooled drum, allowing the thinlayer to remain in contact'with the freezing surface for a length oftime such that, on removing the film from the drum and allowing 'the icetherein to melt, a continuous sheet of completely coagulated materialremained. The sheet was then washed by passing it under sprays of waterwhile supported on a moving belt and dried by passage through a chamberthrough which air heated to 80 C. was passing. The dried material wasthen treated on a rubber mill with 2% of dibenzoyl disulfide.

It plasticized rapidly, giving a plasticity number 1 of 129 with arecovery of 15. Bis-carbo-methoxyphenyl tetrasulfide andbis-thionaphthoyl disulfide gave similar results. Without the additionof disulfide, the plasticity number was 423.

Example 17 more octyl mercaptan being added during the milling. Thecoagulum was observed to be much softer and more easily worked than whenno mercaptan was present and the dried polymer had a plasticity numberof 129 and a recovery of 15. Latex from the same lot worked up inexactly the same way except that no octyl mercaptan was added had aplasticity number of 290. Substitution of paranitrothiophenol,thiobetanaphthol, mercapto dimethylbenzothiazol, thiobenzoic acid andtetramethyl thiuram disulfide for the octyl mercaptan gave plasticitynumbers and recoveries of 154-10, 162-76, 200-143, 175-111, and 196-115,respectively.

' Example 18 Into dryunplasticized polymer, prepared as in Example 16and containing phenyl-beta-naphthylamine but no plasticizing agent, wasincorporated by milling 2% of potassium hexamethylene dithiocarbamate. Aplastic product with a plasticity number of 110 and a recovery of 4 wasobtained. Similar results were obtained with the hexamethyleneimine saltof this acid and with the piperidine (piperidinium) salt of penta-'methylene dithiocarbamate.

' Example 19 The product of Example 10 was heated for 2 days at 70 C.The plasticity and recovery numbers fell from 105-5 to 82-0.

Example 20 Into the product of Example 8,,one part of magnesium oxidewas incorporated by milling. The plasticity rapidly increase-d, theplasticity and recovery numbers falling from 142-16 to 105-6.

Example 21 Into a plastic polymer obtained as in Example 9, one part ofthiobetanaphthol was incorporated by milling. The plasticity andrecovery numbers fell from 134-15'to 89-2.

The plasticizing of the polymer is further illustrated by the followingExamples 22 to 34 in Table II, in which unplasticized polymer preparedas in Example 16 in the form of thin sheets was treated on a rubber millat 50 C. with 2% of tetramethyl thiuram disulflde and the indicatedquantity of various amines.

The plasticizing effect of various compounds of the general formula R-SR1 on polymer to which an amine was also added is illustrated in Examples35 to 44 in Table III. Thepolymer in 7 Table II Compound added inaddition to 2% tetra- Plastlcity ifg methyl thiuram disulfide (milled 1oE min. on 50 0. mill) an covery 22 None 180-82 23 Ethylene diamine80.50%) 94- 1 Oleyl amine (0.52% 100- 2 Bcnzyl amine (0.50%) 136-11Dibutyl amine (0.25% 108- 6 Diethanol amine (0.20%) 154-24 D eyclohexylamine (0.35%)" 124- 7 Dibenzyl amine (0.50%)... 137-21 Piperldine(0.50%) 85- 1 Tributyl amine (0.36%) 114- 2 Dunethyl stearyl amine 58141-22 Para phenylene diamine (0 50%). 137-14 Brucme (0.50%) 142-27 Formany purposes, a polymer made with less sulfur is preferred, thus apolymer made with 0.5% sulfur instead of 0.75% has the advantage that itmaybe readily softened to the plasticity desired for most applications(plasticity numbers between about 80 and about 120) but that there islittle danger of plasticizing it beyond 7 this preferred range bymilling too long or at too high a temperature and further, that thepolymers thus obtained have somewhat better curing properties andtensile strength than those prepared from larger amounts of sulfur.Several examples of the plasticization of polymers of this type aregiven in Table IV. The polymer to be plasticized was prepared exactlylike that used in Tables II and 111 except that only 0.5% of sulfur wasused.

Table IV Plasticity Q P Compounds added 33 1 recovery Tetramethylthiuram disulfide (2'7) 45 {Dibutylamine 1% 106-8 46 'le'tramethylthiuram disulfide 11647 t t tli fitfltitt-r" l enzo zy e 47{Dibutylamine 1 .1- 43 {Dibenzothiazyl disulfide 1024 Diorthotolylguanidlne (2% 49 {Bis-isopropylxanthogen (4% 9H Diorthotolyl guanidine(1.5%). {Bis-ethylthioxanthogen (4%)" 10743 '7 Dlorthotolyl guanidine(1.5%) v On the other hand, it is sometimes desirable to have anextremely plastic polymer which with suitable compounding may be used tomake rubber articles by a process similar to casting rather .than by theconventional technique of rubber manufacture. Such polymers may be madeby polymerizing in the presence of larger quantities of sulfur and thenplasticizing with larger amounts of plasticizing agents. An example ofsuch a procedure is as follows.

Example 51 1 chloroprene was polymerized as in Example 16 except that1.5 parts of sulfur were used. The

sulfur was incorporated by first dissolving it in 3 parts of achlorinated naphthalene (sold under the nameof Halowax 1001) at 125 C.and stirring this hot solution into the chloroprene at 40. The latex wasstabilized with antioxidant,

neutralized, coagulated and reduced to the form of a dried sheet asalready described for the polymer used in the examples of Tables II, IIIand IV. Four percent of tetramethyl-thiuram disulfide was thenincorporated into the dry polymer by milling and the product was thenready for shipment or storage. The final plasticization was carried outby incorporating 2% of diorthotolyl guanldine by milling and allowingthe product to stand for 24 hours. It rapidly became extremely plasticand very clearly showed its fluidproperties by flowing under its ownweight. The plasticity number was approximately 10.

The application of the presentinvention to a somewhat different type ofchloroprene polymer prepared in the presence of sulfur-dioxide isillustrated as follows.

Example 52 100 parts of chloroprene, in which 15 parts of sulfurdioxide, 0.24 part of sulfur and 2 parts of cyclohexanol hadbeendissolved, were dispersedat 10 in 212 parts of water containing 2 partsof the sulfated emulsifying agent described in Example8 and 2 parts ofthe emulsifying agent made from naphthalene sulfonic acids described inExample 16 and .polymerized at 42 until the density was approximately1.084. A dispersion of 1 part of the liquid mixture of antioxidants usedin Example 51, a dispersion of 1 part of tetramethyl-thiuram disulfidein the mixture of emulsifying agents used above and a solution of 1 partof dibutylamine in ethyl alcohol were then added to the latex which wasthen c'oagulated with salt. The polymer was washed with water on acorrugated mill and then dried by milling on a rubber mill in thepresence of. 1 part of phenyl-beta-naphthylamine and 1 part oftetramethyl-thiuram disulfide. The plasticity of the product was 94.Similar results were obtained by using 2 parts of diorthotolyl guanidinein the place of 1 part of dibutylamine but when neither of thesealkaline reagents was added the plasticity was 180. With neithertetrametylthiuram disulfide nor the alkaline reagents, the product hadpractically no plasticity; Because of the presence of combined sulfurdioxide (approximately 6% in the polymer) it showed when compounded andcured a very small absorption of solvents such as kerosene even incomparison with the very good solvent resistance of the chloroprenepolymers prepared according to the other examples.

The scope of the general formula is illustrated by the specificcompounds:

Octyl mercaptan Paranitro thiophenol Thiobetanaphthol Thiobenzoic acidMercaptobenzo thiazol Mercaptodimethyl benzothiazol Sodium dimethyldithiocarbamate Potassium hexamethylene dithiocarbamateHexamethylenelmine salt of hexamethylene dithiocarbamate Piperidine saltof pentamethylene dithiocarbamate Diphenyl disulfide a Dibenzoyldisulfide Bisthionaphthoyl disulfide Tetramethyl thiuram disulfideDipentamethylene thiuram disulfide Dibenzothiazyl disulfideBis-carbomethoxyphenyl disulfide Bis-ethylthioxanthogenBis-isopropylxanthogen given in the above examples. As shown in part bythis list, the nature 'of the groups from which R. and R1 in the generalformula may be selected is subject to great variation without exceedingthe scope of the invention or producing compounds for which the processis inoperable. Thus, the alkyl groups may be straight chain or branched,primary, secondary, or tertiary, saturated or unsaturated, long or shortand include hydro-aromatic groups, such as cyclohexyl. The aryl groupsmay be phenyl, tolyl, xylyl, benzyl, etc. Both the alkyl and aryl groupsmay contain, in addition to carbon and hydrogen, various radicals, suchas nitro, chloro, and carbomethoxy as illustrated above.

The thiazyl group may have the two adjacent carbon atoms forming a partof an aromatic nucleus, which is subject to the same variation as thearyl group discussed above. In the thiocarbamyl group, RRNC(=S)-, thexanthogenyl group RO--CS, and the-thioxanthogenyl group, RS-CS-, theradicals represented by R, and R,v may be either alkyl or aryl of thescope discussed above. Both together may be a divalent group such aspentaor hexamethylene. In the aromatic acyl and thioacyl groups, thearomatic portions are also subject to the same variation as alreadydiscussed. By base-forming radical" is meant an element of the alkali oralkaline earth groups or an ammonium or substituted ammonium group, suchas sodium, potassium, calcium, magnesium, ammonium, tetramethylammonium, piperidinium ((CH2)5NH2-) and the like.

Although many of the compounds in the above list such as thepolysulfides. have symmetrical structures, this is only because suchcompounds are generally more easily prepared than the unsymmetrical onesrepresented by the general formula. Unsymmetrical compounds such as:

Phenyl ethyl disulfide Phenyl naphthyl disulfide Phenyl benzoyldisulfide Benzoyl thiobenzoyl disulfide Phenyl thiocarbamyl disulfideThiobenzoyl thiocarbamyl disulfide h Benzothiazyl benzoyl disulfideBenzothiazyl thiocarbamyl disulfide Dimethyl ethyl phenylthiuramtetrasulfi de obviously have properties similar to those of thecorresponding symmetrical compounds and function similarly in thepresent invention. The free dithiocarbamic, xanthogenic andthioxanthogenic acids included in the general formula are in many casesunstable and are conveniently added in the form of their salts, as themercaptans and thio acids may also be added. These salts are providedfor in the general formula when R1 is a base-forming radical. Stillother agents described by the general formula may b formed in thepresence of the polymer instead of being added as such. Thus, it hasbeen found that when the chloroprene used in making the polymerscontains a substantial amount of dichloro- 1,3-butene-2, the addition ofsodium sulfhydrate to the alkaline polymer latex followed by coagulationafter several hours standing gave a soft coagulum similar to thatobtained in Example 17 and giving a plastic polymer on drying. Thiseffect is believed to be due :to the formation of a chlorobutenylmercaptan.

The greater the total proportion of the compound of the general formulapresent during the milling step, the moreplastic is the final product.The quantity present in Examples 1 to 11 is usually sufficient in thecase of tetramethyl thiuram disulfide but may advantageously beincreased when the polymer is hard to plasticize or when less activecompounds having the general formula are used. Thus, altho the quantityto be used depends greatly upon the reagent as well as upon the effectto be produced, preferred quantities are in general in the range fromabout 0.5 to about 6%. It will nevertheless be understood that theinvention is not intended to be limited to this particular range ofamounts, and that on the contrary the use of both greater and lessamounts is within the scope of the inven tion. All percentages which arementioned herein of agents added to the polymer or to the latex are byweight and are based on the weight of the polymer.

It will also be scription that the compounds of the general formula maybe added to the polymer in any desired manner and at a wide variety ofstages of the process and that part may be added at one stage of thegeneral formula is added at an early stage of the process forconvenience or for some effect it may have in addition to the principalone contemplated by the present invention, it is usually desirable totake into account the. possibility that some of it may have been lostduring processing so that the portion lost may be replaced if it reducesthe amount present below the desired amount.

Polymers of chloroprene prepared in the presence of sulfur may beplasticized by a compound of the general formula in 'the absence of anantioxidant such as phenyl-beta-naphthylamine. It is generallydesirable, however, to have such an antioxidant present duringplasticization to retard or prevent oxidation then or later sinceoxidation tends to cause a decrease in plasticity among other things.

The preferred plasticizing agents, when one of the alkaline auxiliaryagents discussed below is not used, are tetramethyl thiuram disulfide,benzothiazyl disulfide, and thio beta-naphthol, and the groups to whichthey below, i. e., the thiuram sulfides, the thiazyl sulfides, and themercaptans. In the presence of alkaline auxiliary agents, the thiuramand thiazy1 sulfides such as tetramethylthiuram disulfide anddibenzothiazyl disulfide are preferred.

Many of the compounds of the general formula have other desirableeffects, in addition to their plasticizing action. Thus, many of them,particularly the thiuram disulfides, are effective in arrestingpolymerization of the chloroprene when added to the incompletelypolymerized dispersions. The thiuram and thiazyl sulfides, among othergroups, greatly reduce the tendency for the plasticized polymers tobecome less plastic on prolonged storage. Both these effects arediscussed for certain plastic chloroprene polymers in copendingapplications of Walker, Serial Nos. 69,- 740 and 154,212, filedrespectively, March 19, 1936, and July 17, 1937. The effects obtainedwith the polymers of the present invention in this connection areanalogous to those obtainedin the Walker cases with the polymers theredescribed; A third additional effect of the compounds of the generalformula is their effect upon curing properties. This may be either toretard the curing so that the highest tensile strength is obtained withlonger curing times, as is generally the case with the mercaptans, or toaccelerate the curing,

apparent from the above deand part at another. In fact, where a compoundas is the case with certain tmumm disul ndes. Both effects aredesirable. It is therefore often advantageous to use two ormoredifferent com course, been selected as a basis for the descriptionbecause the application of th invention to it is a definitely preferredembodiment.

The conditions described in Examples 1 to 11 for the treatment of thepolymer with the compound of the general formula are usually sufflcientto give a well plasticized product but may be further altered,particularly when a more plastic product is desired. To this end, it isoften advantageous to allow the latex to stand, at normal or elevatedtemperatures, after the addition of the compound of the general formulabut before coagulation or to age the coagulum before washing or milling.Increasing the mechanical work done upon the polymer by increasing thetime or decreasin'g'the temperature "of milling generally also increasesthe plasticity. Thus, milling in the presence of water on corrugated'uneven speed rollscauses the polymer to plasticize both more readilyand more extensively.

Particularly when more than 0.5% of sulfur has been used in thepolymerization of the-chloroprene and a suillcient quantity oftetramethyl thiuram disulfide or similar agent has been added, storageof the plasticized polymer preferably at a somewhat elevatedtemperature. as illustrated in Example 19 brings about a furtherprogressive increase in plasticity. The same treatment reduced theplasticity numbers of the products'oi' Examples 2 and 3 to 71 and 86,

\ respectively. Thus, the ultimate plasticity of .the polymers of thepresent process is materially affected by the aging. conditions ofmilling, or heating to which they are subjected. By proper selection itis possible to produce polymers having any of a wide variety of degreesof plasticity. It will be apparent, of course, that,-since an increasein aging, heating and/or milling tends, generally, to increase theultimate plasticity, a decrease in the aging, heating and/or millingwill tend to decrease the ultimate plasticity. It should be noted,however, that prolonged heating, aging or in some cases even millingbeyond a certain point, which varies in individual cases, increases theplasticity only slightly and may even cause a pronbunced reduction inplasticity.

Incorporation of small quantities of reagents, such as alkalineinorganic compounds and particularly amines which give bases withdissociation constants greater than about 10-, into polymers containingcompounds of the formula R-S-Ri (above identified), has a pronouncedadditional eilect upon the plasticity of these polymers, as illustratedin Examples 20, 22 to 34, inclusive, and 36 to 52, inclusive. -As afurther illustration, the treatment with magnesium oxide described inExample 20 applied to the products 175 of Examples 1, 5, 7, 10, and 11reduced the plasticity numbers to 86, 96, 125, 48, and 90, respectively.In addition to the magnesium oxide used here, 'many other mildlyalkaline substances, such as trisodium phosphate, sodium carbonate,sodium tetra-borate, cadmium oxide and barium carbonate, have a similareffect. The salts of magnesium and cadmium, such as the sulfates andchlorides are also useful for this purpose and exert an effect notonly'when incorporated into the plastic polymer but also when present insmall amounts in the dispersion in which the chloroprene is polymerizedaccording to the method of the Collins application cited above.Quaternary ammonium halides, such as cetyl trimethyl ammonium bromide,also have a pronounced plasticiziing action in some cases.

One per cent of the inorganic compounds mentioned above for furtherplasticizing of the chloroprene polymer are generally preferred. Smallproportions, for example, 0.1% and 0.5%. are effective, although to alesser degree. Much larger proportions, although producing in general agreater initial plasticization, sometimes cause a decrease of plasticityon aging of the polymer. The invention is not intended to be limited tothe particular proportions mentioned,

however, so that the invention includes within its scope the use of bothlarger and smaller amounts.

By increasing the proportion of sulfur used in the polymerization of thechloroprene, still greater plasticization by the amines may be obtained.Thus, using 1' part of sulfur instead of 0.5 part in Example 26 gave aplasticity number of 63 instead of 108. The efiect upon plasticity of an.even larger proportion of sulfur is illustrated in Example 51. Inaddition to the amines listed in Table II above, ammonia, diethyl amine,cyclohexyl amine, hexamethyleneimine, and diphenyl guanidine have alsobeen found effective. It will be noted that many of the amines whichhave a pronounced plasticizing action are included in the generalformula NR1, Ra. Rs, in which R1, R2 and R3 are hydrogen, aliphatic andhydro-aromatic hydrocarbon radicals, two of which together may form adivalent group in which both valences are attached to the nitrogen. Thecondensation products of aldehydes with amines, many of which have beendeveloped as accelerators for the vulcanization of natural rubber, inmany cases function like the amines discussed above when incorporatedinto thechloroprene polymers prepared in the presence of sulfur andcontaining the compounds of the general formula R-S-Ri. Especiallyeffective are (l) the condensation products of aniline and itshomologueswith acetaldewas and the high aliphatic aldehydes and (2) thecondensation products of aliphatic diamines with' aromatic aidehydes.Examples of these groups are the condensation products of aniline withacetaldehyde, hexanal, and ethyl isopropyl acroleln, of hexamethylenediamine with benzaldehyde, and of ethylene diamine with salicylaldehyde. Another group of compounds active in this way is representedby thio-carbanilide' Compounds which liberate amines under theconditions used for plasticlzing the polymers may also be ,used. Anexample of this type of agent is trimethylamine oleate. Practicallyspeaking, diaryl guanidines, such as diorthotolyl g uanidine, are thepreferred amines, since they are nonvolatile and therefore are not loston the hot mill and do not give an odor. Amines which give bases withdissociation constants somewhat less than 10" (10-" or 10-, for example)function to some extent. It is also interesting to note that the pHrange of dilute aqueous solutions of the preferred amines is calculatedto be the same (10-12) as for dilute aqueous solutions of the bestinorganic agents, such as 'MgO and Na-iCOa. Thus, so far as is known,all the alkaline materials which are effective in assisting theplasticizing of the polymer are such that 7 when made up into a 0.01molar solution in water they give a pH between about 10 and about 12.

The amines are preferably added :to the dry polymer on the mill but mayalso be advantageously added to the latex before coagulation.

Dried films (Example 16) may be plasticized by exposure to volatileamines or ammonia in the vapor phase. The preferred alkaline auxiliaryagents are magnesium oxide and the amines, dibutylamine, piperidine andthe diaryl guanidines. The latter for example diorthotolyl guanidine areparticularly preferred for the reasons given above. The preferredquantities of the alkaline auxiliary agents to be employed are fromabout 0.2% to about 3% byweight based on the weight of the polymer butas in the case of the compounds of the general formula the quantities tobe used depend greatly upon the reagent as well as upon the effect to beproduced so that it should be understood that the invention is notintended to be limited to this particular range of amounts and that tothe contrary the use of both greater and less amounts is within thescope of the invention.

The present invention includes within its scope also the use of acombination of methods or of plasticizing agents or of assistants or ofall three.

Combinations frequently are found to be advantageous. Thus, polymersplasticized as in Tables II and III may be further plasticized byheating (see Example 19) for 24 hours at 70 C. or by keeping them atordinary temperature for a month. Longer heating at 70 0., however,sometimes makes them less plastic. Further variations include the use oftwo or more compounds of the general formula given first above, or twoor more alkaline auxiliary agents orboth, with or without any others ofthe above mentioned combinations.

The uses of the products produced according to the present inventionare, in general, the same as those given for the plastic polymersproduced by the process described in Starkweather and Collinsapplication Serial No. 156,518, filed July 30, 1937. The products of thepresent invention, however, are new and. have novel properties whichresult in their being particularly adapted for certain uses, altho, as amatter of fact, the novel properties ofthese products are such as togive them advantages for use generally. Moreover, since the presentinvention furnishes chloroprene polymers of a'much greater range ofplasticity than has hitherto been described, the use of such productsare much more varied and include not only those described in theabove-identified copending application (some of which are mentioned moreparticularly below) but also many new uses which result from the highdegree of plasticity and fluidity which the product may have.

( 1) Production of shaped articles by allowing the compounded polymer toflow into a mold and then curing by heat.

(2) Filling cavities, as in tree surgery, and cracks,

such as expansion joints in concrete pavements.

' (3) As a rubbery adhesive which can be applied without solvent, forexample in making ortificial suede, fur, etc. by impinging fibers uponan adhesive coating of the material and then curing. Another type of useof such a cement is in laying glass bricks and wooden blocks and inplace of putty.

(4) Forv production oft concentrated solutions.

These have the same type of uses as rubber solutions but because oftheir higher solids content, and for lower viscosity, the

former are more economical, more eflective, and easier to apply, and maybe used in many places where rubber solutions are unsatisfactory.

' When used for the purposes already described for chloroprene polymersof other types, the products of the present invention have the followingadvantages:

(1) The plasticity may be varied at the time of compounding, it may bevaried over a wide range, and, for a polymer of given sulfur I contentand method of polymerization, the physical properties after curing areindependent of the extent to which the polymer has been plasticized. v

(2) The processing is easier, since the plasticity may be adjustedexactly to that required (for example, calendering and tubing, whichrequire closely controlled plasticity) for the particular operation, andsince the adhesion of the polymer to itself is much better than in thecase of polymers previously described. Y

(3) Curing is faster and may be carried out at lower temperatures thanin the case .of previously described chloroprene polymers.

(4) The cured products have higher modulus,

tensile strength. and resilience, better resistance to oil, abrasion,and tearing, and lower hysteresis loss and heat build-up thancorresponding stocks made from the previously described polymers.

As illustrative of the superior working properties of these materials,it is pointed out that they can very readily be applied in very thinfilms to cloth. Another example is the ease with which the surfaces ofthe polymer may be united with the application of only slight pressure,even after they have been kept for considerable time at ordinarytemperatures. This latter property is for example of great importance inthe building up of automobile tire casings and results from the factthat the polymer surface'retains a moderateamount of tack even tho keptfor considerable time at room temperature. On the other hand, thetackiness does not increase sufllciently at milling temperatures tocause the polymer to give trouble by sticking to the rubber mill.Another advantage of the polymer when prepared by the preferred method,that is by polymerizing in aqueous emulsion and particularly when thecoagulated polymer is dried by exposing to warm air in thin sheets, isits freedom from any substantial odor.

As indicated above, the products of the invention may be compounded andutilized in any of the ways described or referred to in the Starkweatherand Collins application last identified above for the polymers preparedaccording to that application. An important one of these isto usenatural rubber, for example 25%, with the polymer, whereby products withvaluable combinations of properties may be obtained.

I finally giving a dispersion of plasticized polymer. 7

This may then be used, for example, as an adhesive. The very plasticproducts such as are made according to Example .51 are especiallysuitable for use in the latex form, for example for making 1 artificialsuede and fur.

As already stated, the products of the invention may be compounded andutilized in any of the ways described or referred to in the Starkweatherand Collins application. An important 1 one of these is to use naturalrubber, for example with the polymer, whereby products with 1 valuablecombinations of properties may be obtained.

It is thus obvious that the compositions obtained by incorporating acompound of the gen-' eral formula RS-R1 (explained above) into anon-plastic of chloroprene (or other halogen diene included within thescope of this invention) prepared by polymerizing the chloroprene (orother halogen diene) in the presence of sulfur the polymerized material,the step of adding to are new and useful and have very desirableproperties including in addition to those mentioned 1 above theadvantage that the compositions present fewer difiiculties in shippingsince they are tough and do not tend to run together into a :mass, whenseveral sheets are packed together, to nearly as great an extent as doplastic polymers generally.

may, however, be rendered plastic very readily when desired, accordingto the present invention, which also permits of their being plasticlzedto any of a wide variety of degrees.

These polymer compositions It is apparent that many widely differentembodiments of this invention may be made without departing from thespirit and scope thereof and therefore it is not intended to be limitedexcept as indicated in the appended claims.

I claim:

1. In a process for making plastic, rubber-like materials bypolymerizingchloro-2-butadiene- 1,3

the polymerized material at least one compound of the general formulaRPS-R1 in which R is 55 3a member of the group consisting of alkyl,aryl,

genyl, aromatic acyl and aromatic thioacyl radicals, and R1 is a memberof the group consisting of hydrogen, base-forming -radicals, andradicals represented by s7lR2 in which n is a whole number less than 4and R2 is one of the group represented by R above.

thiazyl, thiocarbamyl, xanthogenyl, thioxantho- 2. In a process formaking plastic, rubber-like materials by polymerizingchloro-2-butadiene-1,3 in the presence of sulfur and then plasticizingthe polymerized material, the steps of adding to the polymerizedmaterial at least one compound of the general formula RSR1 in which R isa member of the group: consisting of alkyl, aryl, thiazyl, thiocarbamyl,xanthogenyl, thioxanthogenyl, aromatic acyl and aromatic thioacylradicals and R1 is a member of the group consisting of hydrogen,base-forming radicals, and radicals represented by '-SnRa in which n isa whole number less than 4 and R2 is one of the group represented by Rabove, and adding an amine which gives a base with a dissociationconstant greater than about 10-.

3. In a process for making plastic, rubber-like materials bypolymerizing chloro-2-butadiene-l,-3 in aqueous emulsion in the presenceof sulfur, coagulating the emulsion, and plasticizing the polymerizedmaterial, the step of adding to the polymerized material at least onecompound of the general formula R-S-Ri in which R is a member of thegroup consisting of alkyl, aryl, thiazyl, thiocarbamyl, xanthogenyl,thioxantho-' genyl, aromatic acyl and aromatic thioacyl radicals, and R1is a member of the group consisting of hydrogen, base-forming radicals,and radicals represented by -S1|R2 in which n is a whole number lessthan 4 and R: is one of the group represented by R above.

4. In a process for making plastic, rubber-like materials bypolymerizing chloro-2-butadiene-1,3 in aqueous emulsion in the presenceof sulfur,

coagulating the emulsion, and plasticizing the polymerized material, thesteps of adding to the polymerized material at least one compound of thegeneral formu1a RS-R1 in which R is a member of the group consisting ofalkyl, aryl, thiazyl, thiocarbamyl, xanthogenyl, thioxanthogenyl,aromatic acyl and aromatic thioacyl radicals and R1 is a member of thegroup consisting of hydrogen, base-forming radicals, and radicalsrepresented by -S"Ra in which n is a whole number less than 4 and R2 isone of the group represented by R above, and adding an amine which givesa base with a dissociation constant greater than about 10*.

5. A composition comprising a polymer of.

chloro-2-butadiene-1,3 having sulfur in chemical combination therewithand at least'one uncombined compound of the general formula RSR1 inwhich R is a member of the group consistingof alkyl, aryl, thiazyl,thiocarbamyl, xanthogenyl, thioxanthogenyl, aromatic acyl and aromaticthioacyl radicals, and R1 is a member of the group consisting ofhydrogen, base-forming radicals, and radicals represented by Sn-R2 inwhich n is a whole number less than 4 and R2 is one of the grouprepresented by R above.

6. A composition comprising a polymer of chloro-2-butadiene-1,3 havingsulfur in chemical combination therewith, at least one uncombinedcompound of the general formula RSR1 in which R is a member of the groupconsisting of alkyl, aryl, thiazyl, thiocarbamyl, xanthogenyl,thioxanthogenyl, aromatic acyl and aromatic thioacyl radicals, and R1 isa member of the group consisting of hydrogen, base-forming radicals, andradicals represented by s1|R2 in which n is a whole number less than 4and R2 is one of the group represented by R above, and an uncombinedamine which gives a base with a dissociation constant greater than about10-.

7. In the process for making plastic, rubberlike materials bypolymerizing chloro-2-butadiene-1,3 in the presence of sulfur and thenplasticizing the polymerized material, the step of adding to thepolymerized material a thiazyl sulfide.

8. In the process for making plastic, rubberlike materials bypolymerizing chloro-2-butacliche-1,3 in the presence of sulfur and thenplasticizing the polymerized material, the step of adding to thepolymerized material benzo- 4 thiazyl sulfide.

9. In the process for making plastic, rubberlike materials bypolymerizing ch1oro-2-butad1- ene-1,3 in the presence of sulfur and thenplasticizing the polymerized material, the step of adding to thepolymerized material a mercaptan.

10. In the process for making plastic, rubberlike materials bypolymerizing chloro-2-butadiene-1,3 in the presence of sulfur and thenplasticizing the polymerized material, the step of adding to thepolymerized material thio-betanaphthol.

11. In the process for making plastic, rubberlike materials bypolymerizing chloro-2-butadiene-1,3 in the presence of sulfur and thenplasticizing the polymerized material, the step of adding to thepolymerized material a thiuram disulflde.

12. In the process for making plastic, rubberlike materials bypolymerizing chloro-2-butadiene-1,3 in the presence of sulfur and thenplasticizing the polymerized material, the step of adding to thepolymerized material a tetra alkyl thiuram disulfide.

13. In the process for making plastic, rubberlike materials bypolymerizing chloro-2-butadiene-1,3 in the presence of sulfur and thenplas-.

ticizing the polymerized material, the step of adding to the polymerizedmaterial a tetra alkyl thiuram disulflde and a. diarylguanidine.

MORTIMER A. YOUKER.

